This invention relates to reversible internal combustion engines.
In many situations where internal combustion engines having a reverse gear are used, it would be a distinct advantage if the engine were capable of reverse rotation, thereby obviating the need for the reverse gear. Such an engine would provide a mechanically simpler and more economically functioning apparatus. Examples of such applications would be in snowmobiles for instance, where it is currently necessary to provide a reverse gear if the snowmobile is to be capable of being backed up. In such an application, it would also be highly desirable that the direction of rotation of the engine be automatically reversible at the touch of a switch, rather than requiring the engine to be stopped and mechanical energy be applied directly to the engine by a starter motor or by the operator through a starter pulley.
Presently available geared systems for reverse drive of snowmobiles are cumbersome and expensive and as a consequence are provided only on high end and on heavy duty, industrial type machines. The present invention is an electronic system without moving parts which achieves the same object of providing reverse drive while being smaller, quieter, simple to use, and more reliable.
It is known in the art to provide an internal combustion engine which is capable of operation in either direction of rotation. It is also known to provide a means of reversing the direction of rotation, either when the engine is stationary or when it is operating. Some prior art devices rely on kickback of the motor during stalling conditions to provide the initial impetus in the reverse direction in order to achieve rotation in the reverse direction.
Generally speaking, there are two basic kinds of arrangements for altering the timing to permit rotation in the reverse direction. The first utilizes a rotary switch which is friction mounted on the drive shaft. When reversal is required, the ignition circuit is disconnected, causing the motor to decelerate. Upon stopping, kickback from the compression in the cylinder causes the engine to reverse rotate, in turn causing the friction mounted switch to toggle, engaging appropriate ignition and timing contacts for rotation in the opposite direction.
The other basic kind of arrangement provides for alteration of the spark advance by means of a "lost motion" mechanism in the timing shaft. Such a mechanism provides a certain amount of slippage in the timing shaft when the motor is turned in an opposite direction, sufficient to establish correct timing for the engine while running in the opposite direction. Canadian Patent 234,069 (Lanham) discloses a reversing mechanism for a 4-cylinder internal combustion engine which operates through a system of sliding gears to reverse the direction of the crank shaft without reversing the direction of the cam shaft and timing shaft. However, this system requires a complex arrangement of gears and furthermore cannot be reversed without first bringing it to a full stop and mechanically sliding a gear.
Canadian Patents 624,450 (Strang) and 594,571 (Rose) are related patents which provide a reversing lever to mechanically move the distributor housing to retard the spark sufficiently to kill the engine. A reverse starting switch is provided to start the motor in the opposite direction and timing is provided by a "lost motion" distributor shaft. Both of these systems rely upon mechanical movement of the distributor housing and a separate action on the part of the operator to commence reverse rotation.
U.S. Pat. No. 2,881,744 (Fox) illustrates a sliding switch type of reversal mechanism. When it is desired to reverse the engine, a switch is thrown disconnecting the ignition circuits. When the motor stops, compression remaining in the cylinder provides a kickback which rotates the rotor slightly in the reverse direction, causing the friction mounted switch on the crankshaft to move into engagement in the opposite direction such that the ignition is re-engaged and rotation commences in the opposite direction. This system relies upon a mechanical disposition of components as in the previous cases discussed.
U.S. Pat. No. 3,189,009 (Andersen) also uses a friction mounted rotary switch similar to U.S. Pat. No. 2,881,744 above. In this case, correct spark advance for each direction of rotation is provided by a separate set of breaker points and arm mounted against a cam on the rotor. These are electrically connected to the ignition system by the rotary switch, depending upon the direction of rotation. As in previous cases, this is a mechanical arrangement and furthermore does not provide a means for controlling the speed of the motor.
U.S. Pat. No. 3,981,278 (Harada) discloses a control system for controlling the operation of reversible marine engines. This system improves upon previous systems by providing circuits for sensing whether or not an engine is running and its speed if running, and by providing a restart delay when reversal is required until the engine speed is reduced to a safe level. However, this is a complex system designed for large marine engines and not readily applicable to small internal combustion engines.
Finally, U.S. Pat. No. 3,088,445 (Gardner) discloses a portable power driven tool which may be operated in either direction of rotation. Separate sets of magnetic pole pieces are located on the rotor in such a fashion that one pole piece in combination with a fixed magnetic means provides the spark in one direction of rotation while the other pair of pole pieces provides the spark with appropriate timing in the opposite direction. However, this patent does not provide for reversal of the motor while in operation, but instead requires the motor to be brought to a full stop and a mechanical starter applied to the motor in the desired direction of rotation to cause it to commence operation. Accordingly, this patent does not disclose a means of reversing the direction of rotation of the motor while it is operating.
From the above analysis, it may be seen that only Fox and Andersen disclose internal combustion engines which may be reversed in direction while operating. However, neither of these provides a simple non-mechanical method of so doing.